I had an idea that I thought was kind of cool that would work if several of us RPG Publishers worked together, and doesn't cost much:
Make the backs of our business cards into connectable dungeon maps. I sell 2.5"x2.5" cards that are connectable dungeon designs that have two corridor openings on each side that can connect to the next one. We could reformat that same idea with either one corridor on each side or one on the short sides and two on the long sides. Dyson Logos said he's done something similar, so we may go with the format he did already. You're free to design a mini-dungeon or cave complex or even a SF space station with the only restriction being those corridors match up.

It could be pretty cool if people could collect business cards from 5-10 of us. The more who participate the better it gets!

Here's how it helps:
-one more reason for people to go to your booth. (We could keep a list of publishers doing this and share it with people as they ask.)
-people are more likely to keep your card and pull it out from time to time.
-the cost is minimal. Business card printers often print 2 sided at the same price as one side, or it is only 10-20% more. And if you want to double your quantity in case this idea takes off, they also only usually charge 30% more. EX: Uprinting is $22 for 1000 front only standard size business cards. $29 for front/back business cards and $41 for 2000 front/back cards.

If we get a few posts here of people interested, I'll post an example.

I'm just an attendee, not an exhibitor, but this sounds like a really cool idea. It seems like it could give me an incentive to keep your business card, and look at it more than once, perhaps even long after the show.

So to expand on your idea, you could do a treasure map/scavenger hunt theme. Each company will have part of the map or a something to do with the scavenger hunt. A person would need to show something the from the prior area to next area to get something to show to the next area.

Maybe pull together as companies to have something special for those that complete all the steps to get a minor prize (a D6? Figure? Collectable pin?).

For any exhibitors waiting until the last minute to do business cards, Dyson Logos has created some business card geomorph maps. You're free (creative commons) to grab one and add it to the back of your business card.

I've got one, but in a different style and in order to connect to our Dungeon Geomorph cards, these are "fat" business cards--3.5" x 2.5" instead of the usual 3.5"x2". The 3.5" sides of mine will connect to what Dyson has done, and the 2.5" side will connect to our Dungeon Geomorph cards (we've got a whole set of 90 2.5"x2.5" cards.)